"Iron Coffins" by Herbert Werner is an excellent account written by a man who was there......

Another outstanding account was "The Laughing Cow" by Jost Metzler. It's a 1955 copy from publisher William Kimber (London) and I found it in a used book shop in Auckland, NZ. Great book, lots of photos.....

I also enjoyed Operation Drumbeat and U-Boat War in the Caribbean..... I'm on my 11-12th U-Boat book from my collection of about 40 books.